Different demographics have different interests, experiences, and knowledge. It's trivially obvious that getting a broader subset of society to contribute will also broaden the content.
With less than 10% of editors being women, for example, content is guaranteed to be somewhat skewed, even assuming absolutely no ill will by anybody.
Among the famous examples are a scientist's entry being deleted as "not notable" just weeks before she won the Nobel Prize. Or, if you prefer quantitative data, that articles about women tend to emphasise their relationships and children (https://arxiv.org/pdf/1501.06307v2.pdf).
Wikipedia wants to be an encyclopedia though, not a bag of personal anecdotes and life experiences.
I read that as wikipedia should be factual and facts don't need to care about the background of the person. Citations are always needed.
Diversity in race imo is a bad diversity criteria for some things. For one, it separates people living long time at a particular place (think 2-3 generations) as different people because they are not white so they must be different.
Anyone who talks about diversity I have seen has stereotypes of their own on what people from different races are like.
The only way to do so is to discard the interests and knowledge while putting great emphasis on experiences - and immediately assume they will end manifest as bulk personal anecdotes.